The present invention relates to systems for delivering positive air pressure through the nasal passages to facilitate treatment of breathing disorders such as sleep apnea, ventilation difficulties or anesthetic gas administration.
Obstructive sleep apnea is caused by obstruction of the of the upper airway during sleep which results in the absence of airflow through the nose or mouth for at least 10 seconds. Obstructive sleep apnea episodes are usually most serve during periods of REM (Rapid Eye Movement) sleep, when muscle tone is inhibited. The upper airway then narrows as a result of the relaxation of a number of muscles. The suction pressure of inspiration then causes further narrowing or collapse of the airway. The lack of airflow causes the oxygen level in the blood to drop causing arousal which then restores upper airway muscle tone allowing normal breathing.
Heavy snoring and daytime sleepiness are the most common symptoms associated with obstructive sleep apnea syndrome. Other complaints include night-time thrashing, sleep walking, enuresis, disorientation, personality changes, intellectual deterioration, sexual dysfunction, hypnagogic hallucinations, automatic behavior and morning headaches. The prevalence of episodes of obstructive apnea and the frequency of occurrence increase with age. Men are much more commonly affected than women and nearly 50% of elderly men have 20 or more apneic episodes each night. Other known risk factors include obesity, chronic alcoholism, chronic obstructive pulmonary disease and postmenopausal state. Altogether more than 30,000 patients are treated each year for obstructive sleep apnea.
The most effective and frequently applied therapy for obstructive sleep apnea is by means of continuous positive airway pressure (CPAP). For such therapy, a patient is fitted with a tight fitting nasal mask connected through an airway to a blower which supplies air at a slight positive pressure to the nasal passages. The application of the slight positive pressure is immediately effective in reversing airway obstruction in most patients with obstructive sleep apnea. Although the therapeutic results of nasal CPAP are often dramatic and immediate, it is only effective when used properly and on a regular basis. Failure to apply nasal CPAP for even a single night results in recurrence of hypersomnolence the next day.
Problems associated with wearing existing masks or positive airway pressure delivery systems during periods of attempted sleep are sufficient to deter many patients from continuing CPAP therapy. Some problems include excessive noise resulting from leaks around improperly fitting masks or general discomfort caused by the design of the mask or the CPAP delivery system.
One conventional mask design includes an air delivery tubing of relatively large diameter connected to the front of a nasal mask through use of a swivel port. Such a tubing assembly is heavy and bulky making it extremely difficult to maintain a mask seal for airway pressure support with head movement during sleep. Any break in the mask seal results in air loss around the edges of the mask causing excessive noise and possibly reducing the positive pressure through the nasal passages to a level insufficient to prevent apneic events.
Another type of CPAP device replaces the mask with nasal prongs or pillows as shown in U.S. Pat. No. 4,782,832. In such a device, a large diameter air delivery tube is positioned in line with the nose across the top of the head and down the center of the forehead to connect to nasal pillows which are inserted in to the patient's nostrils. Placement of the large diameter air delivery tube on the head, makes the system uncomfortable and easy to dislodge with head movement during sleep which can result in displacement of the nasal pillows from the nostrils.